Automated Pattern Fidelity Measurement Plan Generation

ABSTRACT

Methods and systems for determining parameter(s) of a metrology process to be performed on a specimen are provided. One system includes one or more computer subsystems configured for automatically generating regions of interest (Rats) to be measured during a metrology process performed for the specimen with the measurement subsystem based on a design for the specimen. The computer subsystem(s) are also configured for automatically determining parameter(s) of measurement(s) performed in first and second subsets of the ROIs during the metrology process with the measurement subsystem based on portions of the design for the specimen located in the first and second subsets of the ROIs, respectively. The parameter(s) of the measurement(s) performed in the first subset are determined separately and independently of the parameter(s) of the measurement(s) performed in the second subset.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention generally relates to automated pattern fidelitymeasurement plan generation. Certain embodiments relate to methods andsystems for determining one or more parameters of a metrology process tobe performed on a specimen.

2. Description of the Related Art

The following description and examples are not admitted to be prior artby virtue of their inclusion in this section.

Inspection processes are used at various steps during a semiconductormanufacturing process to detect defects on wafers to promote higheryield in the manufacturing process and thus higher profits. Inspectionhas always been an important part of fabricating semiconductor devices.However, as the dimensions of semiconductor devices decrease, inspectionbecomes even more important to the successful manufacture of acceptablesemiconductor devices because smaller defects can cause the devices tofail.

Defect review typically involves re-detecting defects detected as suchby an inspection process and generating additional information about thedefects at a higher resolution using either a high magnification opticalsystem or a scanning electron microscope (SEM). Defect review istherefore performed at discrete locations on the wafer where defectshave been detected by inspection. The higher resolution data for thedefects generated by defect review is more suitable for determiningattributes of the defects such as profile, roughness, more accurate sizeinformation, etc. Since the defect review is performed for defectsdetected on the wafer by inspection, the parameters used for defectreview at a location of a detected defect may be determined based onattributes of the defects determined by the inspection process. However,the output acquisition parameters (e.g., optical, electron beam, etc.parameters) used for defect review at a location of a detected defectare generally not determined based on information about the portion ofthe design in or near the location of the defect because suchinformation is generally irrelevant to the output acquisition functionsperformed for the detected defects during defect review.

Metrology processes are also used at various steps during asemiconductor manufacturing process to monitor and control the process.Metrology processes are different than inspection processes in that,unlike inspection processes in which defects are detected on a wafer,metrology processes are used to measure one or more characteristics ofthe wafer that cannot be determined using currently used inspectiontools. For example, metrology processes are used to measure one or morecharacteristics of a wafer such as a dimension (e.g., line width,thickness, etc.) of features formed on the wafer during a process suchthat the performance of the process can be determined from the one ormore characteristics. In addition, if the one or more characteristics ofthe wafer are unacceptable (e.g., out of a predetermined range for thecharacteristic(s)), the measurements of the one or more characteristicsof the wafer may be used to alter one or more parameters of the processsuch that additional wafers manufactured by the process have acceptablecharacteristic(s).

Metrology processes are also different than defect review processes inthat, unlike defect review processes in which defects that are detectedby inspection are re-visited in defect review, metrology processes maybe performed at locations at which no defect has been detected. In otherwords, unlike defect review, the locations at which a metrology processis performed on a wafer may be independent of the results of aninspection process performed on the wafer. In particular, the locationsat which a metrology process is performed may be selected independentlyof inspection results. In addition, since locations on the wafer atwhich metrology is performed may be selected independently of inspectionresults, unlike defect review in which the locations on the wafer atwhich defect review is to be performed cannot be determined until theinspection results for the wafer are generated and available for use,the locations at which the metrology process is performed may bedetermined before an inspection process has been performed on the wafer.

Current methods used for setting up metrology processes have a number ofdisadvantages. For example, conventional recipe setup for patternmetrology (including, for example, critical dimension (CD) and overlaymeasurements) with a SEM requires prior knowledge of the locations thatare to be measured. In addition, the conventional recipe setup processoften includes the use of the design. Furthermore, if a new pattern ofinterest (POI) is discovered that the user wants to measure once or onan ongoing basis, it requires an update of the metrology tool recipe.

Accordingly, it would be advantageous to develop systems and methods fordetermining one or more parameters of a metrology process to beperformed on a specimen that do not have one or more of thedisadvantages described above.

SUMMARY OF THE INVENTION

The following description of various embodiments is not to be construedin any way as limiting the subject matter of the appended claims.

One embodiment relates to a system configured to determine one or moreparameters of a metrology process to be performed on a specimen. Thesystem includes a measurement subsystem including at least an energysource and a detector. The energy source is configured to generateenergy that is directed to a specimen. The detector is configured todetect energy from the specimen and to generate output responsive to thedetected energy. The system also includes one or more computersubsystems configured for automatically generating regions of interest(ROIs) to be measured during a metrology process performed for thespecimen with the measurement subsystem based on a design for thespecimen. The one or more computer subsystems are also configured forautomatically determining one or more parameters of one or moremeasurements performed in first and second subsets of the ROIs duringthe metrology process with the measurement subsystem based on portionsof the design for the specimen located in the first and second subsetsof the ROIs, respectively. The one or more parameters of the one or moremeasurements performed in the first subset are determined separately andindependently of the one or more parameters of the one or moremeasurements performed in the second subset. The system may be furtherconfigured as described herein.

Another embodiment relates to a computer-implemented method fordetermining one or more parameters of a metrology process to beperformed on a specimen. The method includes the automaticallygenerating and automatically determining steps described above. Thesteps of the method are performed by one or more computer systems.

Each of the steps of the method described above may be further performedas described further herein. In addition, the embodiment of the methoddescribed above may include any other step(s) of any other method(s)described herein. Furthermore, the method described above may beperformed by any of the systems described herein.

Another embodiment relates to a non-transitory computer-readable mediumstoring program instructions executable on a computer system forperforming a computer-implemented method for determining one or moreparameters of a metrology process to be performed on a specimen. Thecomputer-implemented method includes the steps of the method describedabove. The computer-readable medium may be further configured asdescribed herein. The steps of the computer-implemented method may beperformed as described further herein. In addition, thecomputer-implemented method for which the program instructions areexecutable may include any other step(s) of any other method(s)described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages of the present invention will become apparent tothose skilled in the art with the benefit of the following detaileddescription of the preferred embodiments and upon reference to theaccompanying drawings in which:

FIGS. 1 and 2 are schematic diagrams illustrating side views ofembodiments of a system configured as described herein;

FIG. 3 is a schematic diagram illustrating a plan view of one embodimentof the relationship between various terms used herein includingmeasurement site, field of view, and region of interest;

FIG. 4 is a schematic diagram illustrating a plan view of one example ofa portion of a design for a wafer as the portion of the design appearsin design space;

FIG. 5 is a schematic diagram illustrating a plan view of one example ofthe portion of the design shown in FIG. 4 as the portion of the designmay be printed on a wafer;

FIG. 6 is a schematic diagram illustrating a plan view of one embodimentof the portion of the design shown in FIG. 5 with different regions ofinterest within the portion of the design;

FIGS. 7-8 are schematic diagrams illustrating plan views of differentexamples of results of currently used methods for aligning a portion ofa design for a wafer in design space with the portion of the design forthe wafer in wafer space;

FIG. 9 is a schematic diagram illustrating a plan view of one example ofresults of an embodiment for aligning a portion of a design for a waferin design space with the portion of the design for the wafer in waferspace;

FIGS. 10-12 are schematic diagrams illustrating plan views of a portionof a design for a wafer in design and wafer space and how they can bealigned by embodiments described herein;

FIG. 13 is a schematic diagram illustrating a plan view of a portion ofa design for a wafer in wafer space and how the dimensions across whicha measurement may be performed can be determined by embodimentsdescribed herein; and

FIG. 14 is a block diagram illustrating one embodiment of anon-transitory computer-readable medium storing program instructions forcausing a computer system to perform a computer-implemented methoddescribed herein.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and are herein described in detail. The drawingsmay not be to scale. It should be understood, however, that the drawingsand detailed description thereto are not intended to limit the inventionto the particular form disclosed, but on the contrary, the intention isto cover all modifications, equivalents and alternatives falling withinthe spirit and scope of the present invention as defined by the appendedclaims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The terms “design” and “design data” as used herein generally refer tothe physical design (layout) of an IC and data derived from the physicaldesign through complex simulation or simple geometric and Booleanoperations. The physical design may be stored in a data structure suchas a graphical data stream (GDS) file, any other standardmachine-readable file, any other suitable file known in the art, and adesign database. A GDSII file is one of a class of files used for therepresentation of design layout data. Other examples of such filesinclude GL1 and OASIS files and proprietary file formats such as RDFdata, which is proprietary to KLA-Tencor, Milpitas, Calif. In addition,an image of a reticle acquired by a reticle inspection system and/orderivatives thereof can be used as a “proxy” or “proxies” for thedesign. Such a reticle image or a derivative thereof can serve as asubstitute for the design layout in any embodiments described hereinthat use a design. The design may include any other design data ordesign data proxies described in commonly owned U.S. Pat. No. 7,570,796issued on Aug. 4, 2009 to Zafar et al. and U.S. Pat. No. 7,676,077issued on Mar. 9, 2010 to Kulkarni et al., both of which areincorporated by reference as if fully set forth herein. In addition, thedesign data can be standard cell library data, integrated layout data,design data for one or more layers, derivatives of the design data, andfull or partial chip design data.

In some instances, simulated or acquired images from a wafer or reticlecan be used as a proxy for the design. Image analysis can also be usedas a proxy for design analysis. For example, polygons in the design maybe extracted from an image of a design printed on a wafer and/orreticle, assuming that the image of the wafer and/or reticle is acquiredwith sufficient resolution to adequately image the polygons of thedesign. In addition, the “design” and “design data” described hereinrefers to information and data that is generated by semiconductor devicedesigners in a design process and is therefore available for use in theembodiments described herein well in advance of printing of the designon any physical wafers.

Preferably, the “design” or “physical design” as those terms are usedherein refer to the design as it would be ideally formed on the wafer.In this manner, a design or physical design described herein wouldpreferably not include features of the design that would not be printedon the wafer such as optical proximity correction (OPC) features, whichare added to the design to enhance printing of the features on the waferwithout actually being printed themselves. In this manner, in someembodiments, the design for the specimen used for the automaticallygenerating and the automatically determining steps described furtherherein does not include features of the design that will not be printedon the specimen.

Turning now to the drawings, it is noted that the figures are not drawnto scale. In particular, the scale of some of the elements of thefigures is greatly exaggerated to emphasize characteristics of theelements. It is also noted that the figures are not drawn to the samescale. Elements shown in more than one figure that may be similarlyconfigured have been indicated using the same reference numerals. Unlessotherwise noted herein, any of the elements described and shown mayinclude any suitable commercially available elements.

One embodiment relates to a system configured to determine one or moreparameters of a metrology process to be performed on a specimen. In oneembodiment, the specimen includes a wafer. In another embodiment, thespecimen includes a reticle. The wafer and the reticle may include anywafer and reticle known in the art.

One embodiment of such a system is shown in FIG. 1. The system includesa measurement subsystem that includes at least an energy source and adetector. The energy source is configured to generate energy that isdirected to a specimen. The detector is configured to detect energy fromthe specimen and to generate output responsive to the detected energy.

In one embodiment, the energy directed to the specimen includes light,and the energy detected from the specimen includes light. For example,in the embodiment of the system shown in FIG. 1, measurement subsystem10 includes an illumination subsystem configured to direct light tospecimen 14. The illumination subsystem includes at least one lightsource. For example, as shown in FIG. 1, the illumination subsystemincludes light source 16. In one embodiment, the illumination subsystemis configured to direct the light to the specimen at one or more anglesof incidence, which may include one or more oblique angles and/or one ormore normal angles. For example, as shown in FIG. 1, light from lightsource 16 is directed through optical element 18 and then lens 20 tobeam splitter 21, which directs the light to specimen 14 at a normalangle of incidence. The angle of incidence may include any suitableangle of incidence, which may vary depending on, for instance,characteristics of the specimen and the defects to he detected on thespecimen.

The illumination subsystem may be configured to direct the light to thespecimen at different angles of incidence at different times. Forexample, the measurement subsystem may be configured to alter one ormore characteristics of one or more elements of the illuminationsubsystem such that the light can be directed to the specimen at anangle of incidence that is different than that shown in FIG. 1. In onesuch example, the measurement subsystem may be configured to move lightsource 16, optical element 18, and lens 20 such that the light isdirected to the specimen at a different angle of incidence.

In some instances, the measurement subsystem may be configured to directlight to the specimen at more than one angle of incidence at the sametime. For example, the illumination subsystem may include more than oneillumination channel, one of the illumination channels may include lightsource 16, optical element 18, and lens 20 as shown in FIG. 1 andanother of the illumination channels (not shown) may include similarelements, which may be configured differently or the same, or mayinclude at least a light source and possibly one or more othercomponents such as those described further herein. If such light isdirected to the specimen at the same time as the other light, one ormore characteristics (e.g., wavelength, polarization, etc.) of the lightdirected to the specimen at different angles of incidence may bedifferent such that light resulting from illumination of the specimen atthe different angles of incidence can be discriminated from each otherat the detector(s).

In another instance, the illumination subsystem may include only onelight source (e.g., source 16 shown in FIG. 1) and light from the lightsource may be separated into different optical paths (e.g., based onwavelength, polarization, etc.) by one or more optical elements (notshown) of the illumination subsystem. Light in each of the differentoptical paths may then be directed to the specimen. Multipleillumination channels may be configured to direct light to the specimenat the same time or at different times (e.g., when differentillumination channels are used to sequentially illuminate the specimen).In another instance, the same illumination channel may be configured todirect light to the specimen with different characteristics at differenttimes. For example, in some instances, optical element 18 may beconfigured as a spectral filter and the properties of the spectralfilter can be changed in a variety of different ways (e.g., by changingthe spectral filter) such that different wavelengths of light can bedirected to the specimen at different times. The illumination subsystemmay have any other suitable configuration known in the art for directingthe light having different or the same characteristics to the specimenat different or the same angles of incidence sequentially orsimultaneously.

In one embodiment, light source 16 may include a broadband plasma (BBP))light source. In this manner, the light generated by the light sourceand directed to the specimen may include broadband light. However, thelight source may include any other suitable light source such as alaser. The laser may include any suitable laser known in the art and maybe configured to generate light at any suitable wavelength orwavelengths known in the art. In addition, the laser may be configuredto generate light that is monochromatic or nearly-monochromatic. In thismanner, the laser may be a narrowband laser. The light source may alsoinclude a polychromatic light source that generates light at multiplediscrete wavelengths or wavebands.

Light from optical element 18 may be focused to beam splitter 21 by lens20. Although lens 20 is shown in FIG. 1 as a single refractive opticalelement, it is to be understood that, in practice, lens 20 may include anumber of refractive and/or reflective optical elements that incombination focus the light from the optical element to the specimen.The illumination subsystem shown in FIG. 1 and described herein mayinclude any other suitable optical elements (not shown). Examples ofsuch optical elements include, but are not limited to, polarizingcomponent(s), spectral filter(s), spatial filter(s), reflective opticalelement(s), apodizer(s), beam splitter(s), aperture(s), and the like,which may include any such suitable optical elements known in the art.In addition, the system may be configured to alter one or more of theelements of the illumination subsystem based on the type of illuminationto be used for metrology.

The measurement subsystem may also include a scanning subsystemconfigured to cause the light to be scanned over the specimen. Forexample, the measurement subsystem may include stage 22 on whichspecimen 14 is disposed during measurement. The scanning subsystem mayinclude any suitable mechanical and/or robotic assembly (that includesstage 22) that can be configured to move the specimen such that thelight can be scanned over the specimen. In addition, or alternatively,the measurement subsystem may be configured such that one or moreoptical elements of the measurement subsystem perform some scanning ofthe light over the specimen. The light may be scanned over the specimenin any suitable fashion.

The measurement subsystem further includes one or more detectionchannels. At least one of the one or more detection channels includes adetector configured to detect light from the specimen due toillumination of the specimen by the measurement subsystem and togenerate output responsive to the detected light. For example, themeasurement subsystem shown in FIG. 1 includes two detection channels,one formed by collector 24, element 26, and detector 28 and anotherformed by collector 30, element 32, and detector 34. As shown in FIG. 1,the two detection channels are configured to collect and detect light atdifferent angles of collection. In some instances, one detection channelis configured to detect specularly reflected light, and the otherdetection channel is configured to detect light that is not specularlyreflected (e.g., scattered, diffracted, etc.) from the specimen.However, two or more of the detection channels may be configured todetect, the same type of light from the specimen (e.g., specularlyreflected light). Although FIG. 1 shows an embodiment of the measurementsubsystem that includes two detection channels, the measurementsubsystem may include a different number of detection channels (e.g.,only one detection channel or two or more detection channels). Althougheach of the collectors are shown in FIG. 1 as single refractive opticalelements, it is to be understood that each of the collectors may includeone or more refractive optical clement(s) and/or one or more reflectiveoptical element(s).

The one or more detection channels may include any suitable detectorsknown in the art. For example, the detectors may includephoto-multiplier tubes (PMTs), charge coupled devices (CCDs), and timedelay integration (TDI) cameras. The detectors may also include anyother suitable detectors known in the art. The detectors may alsoinclude non-imaging detectors or imaging detectors. In this manner, ifthe detectors are non-imaging detectors, each of the detectors may beconfigured to detect certain characteristics of the scattered light suchas intensity but may not be configured to detect such characteristics asa function of position within the imaging plane. As such, the outputthat is generated by each of the detectors included in each of thedetection channels of the measurement system may be signals or data, butnot image signals or image data. In such instances, a computer subsystemsuch as computer subsystem 36 of the system may be configured togenerate images of the specimen from the non-imaging output of thedetectors. However, in other instances, the detectors may be configuredas imaging detectors that are configured to generate imaging signals orimage data. Therefore, the system may be configured to generate theimages described herein in a number of ways.

It is noted that FIG. 1 is provided herein to generally illustrate aconfiguration of a measurement subsystem that may be included in thesystem embodiments described herein. Obviously, the measurementsubsystem configuration described herein may be altered to optimize theperformance of the system as is normally performed when designing acommercial metrology system. In addition, the systems described hereinmay be implemented using an existing metrology system (e.g., by addingfunctionality described herein to an existing metrology system) such asthe SpectraShape family of tools and the Archer series of tools that arecommercially available from KLA-Tencor. For some such systems, themethods described herein may be provided as optional functionality ofthe metrology system (e.g., in addition to other functionality of themetrology system). Alternatively, the metrology system described hereinmay be designed “from scratch” to provide a completely new metrologysystem.

Computer subsystem 36 of the system may be coupled to the detectors ofthe measurement subsystem in any suitable manner (e.g., via one or moretransmission media, which may include “wired” and/or “wireless”transmission media) such that the computer subsystem can receive theoutput generated by the detectors during scanning of the specimen.Computer subsystem 36 may be configured to perform a number functionsusing the output of the detectors as described herein and any otherfunctions described further herein. This computer subsystem may befurther configured as described herein.

This computer subsystem (as well as other computer subsystems describedherein) may also be referred to herein as computer system(s). Each ofthe computer subsystem(s) or system(s) described herein may take variousforms, including a personal computer system, image computer, mainframecomputer system, workstation, network appliance, Internet appliance, orother device. In general, the term “computer system” may be broadlydefined to encompass any device having one or more processors, whichexecutes instructions from a memory medium. The computer subsystem(s) orsystem(s) may also include any suitable processor known in the art suchas a parallel processor. In addition, the computer subsystem(s) orsystem(s) may include a computer platform with high speed processing andsoftware, either as a standalone or a networked tool.

If the system includes more than one computer subsystem, then thedifferent computer subsystems may be coupled to each other such thatimages, data, information, instructions, etc. can be sent between thecomputer subsystems as described further herein. For example, computersubsystem 36 may be coupled to computer subsystem(s) 102 (as shown bythe dashed line in FIG. 1) by any suitable transmission media, which mayinclude any suitable wired and/or wireless transmission media known inthe art. Two or more of such computer subsystems may also be effectivelycoupled by a shared computer-readable storage medium (not shown).

Although the measurement subsystem is described above as being anoptical or light-based measurement subsystem, the measurement subsystemmay be an electron beam-based measurement subsystem. For example, in oneembodiment, the energy directed to the specimen includes electrons, andthe energy detected from the specimen includes electrons. In thismanner, the energy source may be an electron beam source. In one suchembodiment shown in FIG. 2, the measurement subsystem includes electroncolumn 122, which is coupled to computer subsystem 124.

As also shown in FIG. 2, the electron column includes electron beamsource 126 configured to generate electrons that are focused to specimen128 by one or more elements 130. The electron beam source may include,for example, a cathode source or emitter tip, and one or more elements130 may include, for example, a gun lens, an anode, a beam limitingaperture, a gate valve, a beam current selection aperture, an objectivelens, and a scanning subsystem, all of which may include any suchsuitable elements known in the art.

Electrons returned from the specimen (e.g., secondary electrons) may befocused by one or more elements 132 to detector 134. One or moreelements 132 may include, for example, a scanning subsystem, which maybe the same scanning subsystem included in element(s) 130.

The electron column may include any other suitable elements known in theart. In addition, the electron column may be further configured asdescribed in U.S. Pat. No. 8,664,594 issued Apr. 4, 2014 to Jiang etal., U.S. Pat. No. 8,692,204 issued Apr. 8, 2014 to Kojima et al., U.S.Pat. No. 8,698,093 issued Apr. 15, 2014 to Gubbens et al., and U.S. Pat.No. 8,716,662 issued May 6, 2014 to MacDonald et al., which areincorporated by reference as if fully set forth herein.

Although the electron column is shown in FIG. 2 as being configured suchthat the electrons are directed to the specimen at an oblique angle ofincidence and are scattered from the specimen at another oblique angle,it is to be understood that the electron beam may be directed to andscattered from the specimen at any suitable angles. In addition, theelectron beam-based measurement subsystem may be configured to usemultiple modes to generate images of the specimen (e.g., with differentillumination angles, collection angles, etc.), The multiple modes of theelectron beam-based measurement subsystem may be different in any imagegeneration parameters of the measurement subsystem.

Computer subsystem 124 may be coupled to detector 134 as describedabove. The detector may detect electrons returned from the surface ofthe specimen thereby forming electron beam images of the specimen. Theelectron beam images may include any suitable electron beam images.Computer subsystem 124 may be configured to perform any of the functionsdescribed herein using the output of the detector and/or the electronbeam images. Computer subsystem 124 may be configured to perform anyadditional step(s) described herein. A system that includes themeasurement subsystem shown in FIG. 2 may be further configured asdescribed herein.

It is noted that FIG. 2 is provided herein to generally illustrate aconfiguration of an electron beam-based measurement subsystem that maybe included in the embodiments described herein, As with the opticalmeasurement subsystem described above, the electron beam-basedmeasurement subsystem configuration described herein may be altered tooptimize the performance of the measurement subsystem as is normallyperformed when designing a commercial metrology system. In addition, thesystems described herein may be implemented using an existing metrologyor high resolution defect review system (e.g., by adding functionalitydescribed herein to an existing metrology system) such as the eDR-xxxxseries of tools that are commercially available from KLA-Tencor. Forsome such systems, the methods described herein may be provided asoptional functionality of the system (e.g., in addition to otherfunctionality of the system). Alternatively, the system described hereinmay be designed “from scratch” to provide a completely new system.

Although the measurement subsystem is described above as being alight-based or electron beam-based measurement subsystem, themeasurement subsystem may be an ion beam-based measurement subsystem,Such a measurement subsystem may be configured as shown in FIG. 2 exceptthat the electron beam source may be replaced with any suitable ion beamsource known in the art. In addition, the measurement subsystem may beany other suitable ion beam-based measurement subsystem such as thoseincluded in commercially available focused ion beam (FIB) systems,helium ion microscopy (HIM) systems, and secondary ion mass spectroscopy(SIMS) systems.

The one or more computer subsystems included in the system embodimentsdescribed herein are configured for automatically generating regions ofinterest (ROIs) to be measured during a metrology process performed forthe specimen with the measurement subsystem based on a design for thespecimen. Since the ROIs are determined based on the design for thespecimen, the ROIs may be referred to as “design -based ROIs.” Inaddition, the metrology process for Which one or more parameters aredetermined as described herein may be referred to as a “design drivenmetrology process.”

FIG. 3 provides some context for various terms used herein includingROI. For example, FIG. 3 shows field of view (FOV) 300 for a measurementsubsystem such as one of those described herein centered on measurementsite 302. The measurement site may be a site of a detected defect(detected by inspection and/or review) or a sampled site. Each FOVlocation on the water during a metrology process may be associated withonly one of the measurement sites for which the metrology process willbe performed. For example, during a metrology process, a scanningelectron microscope (SEM) or other measurement subsystem may drive frommeasurement site to measurement site.

As also shown in FIG. 3, within FOV 300, there may be located multipleROIs 304, 306, and 308. Although three ROIs are shown in FIG. 3, theremay be any number of ROIs in any one FOV (i.e., one or more ROIs). Asfurther shown in FIG. 3, the ROIs may be located in a variety oflocations within the FOV, and although the three ROIs are shown as notoverlapping in the FOV, the ROIs may in some instances overlap to someextent in the FOV. Within each of the ROIs, at least one measurement maybe selected to be performed, which may be automatically selected ordetermined as described further herein. Although FIG. 3 does not shownany patterned features that would be formed in the area of the waferlocated in the FOV shown in FIG. 3, the measurements will generally befor one or more characteristics of the patterned features.

To illustrate different measurements that may be performed in differentROIs, FIG. 3 illustrates these different measurements abstractly asdouble headed arrows showing the extent and direction of the dimensionacross which such measurements may be performed. For example, as shownin FIG. 3, measurement 310 may be performed in ROI 304 in one directionacross only a portion of an entire dimension of the ROI in thatdirection. Measurement 312 may be performed in ROI 306 in a differentdirection across an entire dimension of the ROI in that direction. Inaddition, measurements 314 and 316 may be performed in perpendiculardirections across ROI 308. Measurement 314 may be performed across onlya portion of an entire dimension of the ROI in the direction of thatmeasurement while measurement 316 may be performed across an entiredimension of the ROI in the direction of that measurement. Therefore, asdescribed further herein, different measurements may be performed indifferent ROIs, and the measurements performed in any one ROI may beselected or determined as described further herein.

The one or more computer subsystems are also configured forautomatically determining one or more parameters of one or moremeasurements performed in first and second subsets of the ROIs duringthe metrology process with the measurement subsystem based on portionsof the design for the specimen located in the first and second subsetsof the ROIs, respectively. The one or more parameters of the one or moremeasurements performed in the first subset are determined separately andindependently of the one or more parameters of the one or moremeasurements performed in the second subset. In other words, the one ormore parameters may be determined for the first subset of the ROIs basedon only the portion of the design located in the first subset, the oneor more parameters may be determined for the second subset of the ROIsbased on only the portion of the design located in the second subset,and so on. In addition, although some embodiments are described hereinwith respect to first and second subsets, it is to be understood thatthe step(s) performed by the computer subsystem(s) may be performed formore than two subsets of the ROIs (e.g., two or more subsets of ROIs).Furthermore, each of the subsets of the ROIs may include one or moreROIs. For example, the first subset of the ROIs may include only one ROIwhile the second subset of the ROIs may include more than one ROI. Inthis manner, the embodiments described herein are configured forautomated pattern fidelity measurement plan generation. The embodimentsdescribed herein may also be configured for execution of the patternfidelity measurement plans that are generated.

In one embodiment, the automatically generating and the automaticallydetermining are performed during setup of the metrology process. In thismanner, the method may include automatic ROI generation during setupusing the physical design for the wafer. In addition, recipe setup forpattern fidelity measurements may be fully automated since ROIs forthousands of unique sites can be automatically generated during setup.

In another embodiment, the automatically generating and theautomatically determining are performed on-the-fly during runtime of themetrology process. In this manner, the embodiments described herein maybe configured for automated on-the-fly pattern fidelity measurement plangeneration. In addition, the method may include automatic ROI generationduring runtime using the physical design for the wafer.

The embodiments described herein also can generate a metrologymeasurement plan without the need to have prior knowledge of thestructures to be measured. For example, the embodiments described hereindo not necessarily perform functions using information generated byanother system or method for the structures to be measured. Therefore,the embodiments described herein provide a number of advantages overcurrently used methods and systems for measurement plan generation. Forexample, at new process nodes, pattern deviations detected by inspectiontools will require quantitative analysis to determine whether they meetthe criteria of being a “defect.” One cannot anticipate in advance wherethese defect candidates may appear, thus the need for automatedmetrology plan generation on-the-fly.

In some embodiments, the automatically generating includes performingrules -based searching of the design during setup of the metrologyprocess. For example, recipe setup for pattern fidelity measurements canbe fully automated since ROIs for thousands of unique sites can beautomatically generated using a rules-based search of the physicaldesign for the wafer during setup. In this manner, the embodimentsdescribed herein may be configured for rule-based automatic ROIgeneration.

Applying rules for ROI generation to a design may be performed in anumber of different ways. For example, a rule-based approach may be anon-image processing approach in which rules are applied to design datato generate the ROIs. Such applying may be performed using CAD software.In another example, an image processing based approach may be used whichmay include rendering of the design data as an image and then usingimage processing algorithms to generate ROIs using rules as input. Inthis manner, the design data may be consumed by various types of designanalysis software and/or algorithms in order to generate ROIs usingrules as input.

In one embodiment of a rule-based search for automatically generatingthe ROIs, one rule may be created for each different measurement type.In other words, rule 1may be for measurement type 1, rule 2 may be formeasurement type 2, and so on. In addition, each rule may not be formore than one measurement type. In this manner, each rule may define thecharacteristics of the pattern in the design to be formed on the waferthat would make a measurement of its measurement type suitable for thatpattern. For example, a rule for a line width measurement type may bedesigned to identify patterns or portions of patterns that have asubstantially uniform dimension across a relatively large section of thepatterns as candidates for line width measurement types.

In some such instances, each of the rules may be performed for anyand/or all of the patterns included in any one FOV. Therefore, all ofthe rules may be executed on a per FOV basis. Since each rule mayidentify possible locations for measurements of the type for which itwas written, each rule may identify a number of possible ROIs for thatFOV, where each potential location for a measurement type corresponds toone of the ROIs. Therefore, the results of applying each rule to eachFOV may include one or more ROI locations in the FOV. As such, applyingmultiple rules to each FOV may produce one or more ROI locations in eachFOV, some of which may correspond to different measurement types. Insome such instances, each of the ROI locations within the FOV maycorrespond to only one measurement of only one type. However, it ispossible that multiple ROI locations within a FOV may overlap (partiallyor completely) with each other within the FOV (e.g., when it isappropriate to perform two different measurements of two different typesin the same portion of the FOV). In such instances, of the overlappingROIs, each individual ROI may correspond to only one measurement of onlyone measurement type. In other words, there may be only one measurementtype per ROI. Therefore, in order to perform multiple measurements for agiven ROI location, there may be multiple ROIs created, with each ROIhaving the same ROI bounds (or location, coordinates, etc.) but eachhaving different measurement types.

To summarize, therefore, for any one measurement site on a wafer, oneFOV may be designated for that measurement site. All rules may be runfor each FOV, As a result of running all of the rules, one or more ROIsper rule per FOV may be generated with one measurement per ROI. The samesteps may be repeated for each FOV/measurement site until all of theFOVs/measurement sites have been processed.

In one embodiment, the one or more computer subsystems include acomputer subsystem of an electronic design automation (EDA) tool. Forexample, for ROI generation at runtime, the method may use EDA physicaldesign analysis tools or apply custom algorithms to the physical design.In some such instances, a design clip or another representation of thedesign may be automatically analyzed by physical design analysissoftware to determine the valid measurements within the design clip orother representation of the design. In one such example, for ROIgeneration at runtime, an algorithm may automatically segment the designbased on whether a given segment of the pattern is straight/parallel(i.e., the two edges of a structure/pattern are parallel to each other),curved (e.g., on a corner), or at the end of a line. The EDA tool mayinclude any suitable commercially available EDA tool. In some suchembodiments, one or more of the computer subsystems described herein(e.g., computer subsystem(s) 102) may be configured as an FDA tool.

In another embodiment, the one or more parameters automaticallydetermined for the first subset of the ROIs result in a first type ofthe measurement(s) performed in the first subset of the ROIs, the one ormore parameters automatically determined for the second subset of theROIs result in a second type of the measurement(s) performed in thesecond subset of the ROIs, and the first and second types of themeasurement(s) are different from each other. In this manner, the methodmay include automatic determination of measurement type during the ROIgeneration process. There may be one measurement type per ROI and may beautomatically determined during the ROI generation process. As such, theembodiments described herein may be configured for automatic generationof metrology plans with appropriate measurement types for each ROI. Forexample, the metrology plan generation may include, for each FOV,automatically defining ROIs and measurement type from the physicaldesign. Automatically defining the ROIs and the measurement type may beperformed using design analysis algorithms and software. The one or moreparameters may also include where in the ROI that the measurement typeis to be performed. The location in the ROI where the measurement typeis to be performed may be determined as described further herein.

The metrology processes described herein may be performed to determinehow patterns on a wafer differ from the patterns in the design. Inparticular, the patterns as they are designed to be printed on a waferare almost never printed on the wafer exactly as they are designed. Suchdifferences in the as-designed patterns from the as-printed patterns canbe due to the inherent limitations in the processes, tools, andmaterials used to print the patterns on the wafer as well as any errorsin the processes, tools, and materials.

One example of how patterns printed on a wafer can be different frompatterns as -designed is shown in FIGS. 4 and 5. In particular, as shownin FIG. 4, portion 400 of a design for a wafer (not shown in FIG. 4) mayinclude three different patterns 402, 404, and 406. Pattern 402 is anexample of a line structure that may be included in a design for awafer. Pattern 404 is an example of a contact structure that may beincluded in a design for a wafer, and pattern 406 is an example of apolygon structure that may be included in a design for a wafer.

Although some examples of structures that may be included in a designfor a wafer are shown in FIG. 4 (and other figures described herein),the examples are not meant to be representative of any particular designfor any particular wafer. Instead, as will be clear to one of ordinaryskill in the art, the design for the wafer may include many differenttypes of structures in many different arrangements and in many differentnumbers. The structures shown in FIG. 4 (and other figures describedherein) are merely meant to illustrate some hypothetical waferstructures to further understanding of various embodiments describedherein.

Due to the inherent limitations of the tools, materials, and processesused to print the structures shown in portion 400 of the design, thestructures will not necessarily be printed on the wafer as they areincluded in the design. For example, as shown in FIG. 5, instead ofpatterns 402, 404, and 406 in portion 400 having sharp, 90 degreecorners as shown in the design, the patterns will have at least somewhatrounded corners. In addition, any of the structures may have variationsin dimensions such as width at various points across the structures. Forexample, as shown in FIG. 5, pattern 406 has some line width variationscompared to the design characteristics of this structure at multiplepoints across the structure.

The ROIs and measurement type per ROI may therefore be selectedautomatically as described herein based on the characteristics of theas-designed patterns, possibly in combination with some a prioriknowledge of the potential issues with the patterns. A number ofpossible ROIs are shown in FIG. 6 for the patterns shown in FIG. 5.Although these possible ROIs are shown with respect to the patternsshown in FIG. 5, the ROIs may actually be determined based on the designcorresponding to the patterns shown in FIG. 5, i.e., based on thepatterns as they are shown in FIG. 4.

In the embodiment shown in FIG. 6, ROIs 600, 602, and 604 may bedetermined for portions of the features that are designed to havesubstantially uniform dimensions across a portion of the features. Forexample, ROI 600 may be generated for a portion of feature 402 designedto have substantially uniform dimensions across that portion, and. ROIs602 and 604 may be generated for portions of feature 406 designed tohave substantially uniform dimensions across those portions. Themeasurement type automatically selected for these ROIs may be a linewidth measurement, Which may be used to detect necking or bulging issuesin the patterned features.

Another ROI, ROI 606, may be generated automatically for a space betweentwo of the features, features 402 and 406, that is designed to havesubstantially the same dimensions across the ROI. The measurement. typeautomatically selected for this ROI by the embodiments described hereinmay include a gap measurement (or a distance or some statistical measureof distance between the two features). Gap measurements may be performedto detect bridging issues between two patterned features.

The embodiments described herein may also be configured to automaticallygenerate a number of ROIs at and/or near the ends of one or more of thefeatures. For example, as shown in FIG. 6, ROIs 608 and 610 may beautomatically generated for the ends of feature 402 while ROIs 612 and614 may be automatically generated for the ends of feature 406. Themeasurement type selected for these ROIs may be line end position, lineend pullback, line end distance (e.g., distance between the two lineends of a straight line) or some other measurement type that can be usedto describe the relative position of the end of the feature as-designedversus as-printed.

One or more ROIs may also be generated automatically for the corner ofone or more of the patterned features in the design. For example, asshown in FIG. 6, ROIs 616 and 618 may be generated for corners offeature 406. The measurement type selected for these ROIs may becurvature, radius, distance, arc area, or some other measurement typethat can be used to describe the shape of the corner.

Another ROI may be generated automatically by the embodiments describedherein for the contact patterned feature in the design. For example, asshown in FIG. 6, ROI 620 may be generated for contact feature 404, Themeasurement type selected for this ROI may be diameter, width, height,radius, area, or another measurement type that can be used to describehow the contact as-printed is different from the contact as -designed.

Other measurement types that may be determined for a metrology processinclude tip-to-tip (a measurement of the gap between two line ends),tip-line (a measurement of the gap between a line end and a line), linelength (a measurement of the length of a straight line), andcorner-to-corner measurements.

As described above, therefore, the embodiments described herein may beconfigured to perform design-based segmentation of at least a portion ofa design for a wafer into ROIs for a metrology process. In addition,some of the segments may include straight line segments, straight gapsegments, line end segments, corner segments, and contact segments. Thedifferent segments and corresponding ROIs may be determined in thedesign in a number of different ways described herein. For example, thesegments or ROIs may be determined by applying one or more rules to thedesign. In another example, imaginary center lines (imaginary in thesense that they are not part of the design or printed on the wafer)through patterned features in the design may be identified as describedfurther herein and then those center lines can be used to segment thepatterned features into segments and/or ROIs. For example, a straightcenter line through a patterned feature may be used to identify theportion of the patterned feature through which the straight center lineruns as a straight line segment. In another example, a straight centerline through a space between two patterned features may be used toidentify the portion of the space through which that straight centerline runs as a straight gap segment, In an additional example, a portionof a patterned feature in which two straight lines meet at a 90 degreeangle may be identified as a corner segment. Other segments describedherein can be identified in a similar manner using the imaginary centerlines.

Once the various locations for the metrology process have beendetermined (e.g., measurement site locations, alignment site locations,auto-focus site locations, etc.), the metrology recipe setup may includevarious additional steps, some of which may be performed on themetrology tool using a physical wafer. For example, one or more of thelocations may be positioned in a FOV of the measurement subsystem. Oncethe one or more locations are positioned in the FOV of the measurementsubsystem, output of the measurement subsystem may be generated usingdifferent values for parameters of the measurement subsystem, i.e.,optical, electron beam, or imaging parameters. Different outputgenerated using different values of the parameters may then be comparedto determine which of the parameters are best for use in the metrologyprocess for the one or more locations. In addition, differentmeasurement subsystem parameters may be selected for different locationsthat will be measured in the same metrology process. For example, oneset of measurement subsystem parameters may be determined to be the best(and therefore selected) for one measurement type in one type of ROIwhile another, different set of measurement subsystem parameters may bedetermined to be the best (and therefore selected) for another,different measurement type in another, different type of ROI. In asimilar manner, one or more parameters of one or more methods and/oralgorithms applied by the computer subsystem(s) to the output generatedby the measurement subsystem may be determined on a locationtype-by-location type basis (such that different methods and/oralgorithms and/or different parameters of the same method(s) and/oralgorithm(s) may be applied to the output generated at different typesof locations on the wafer).

In some embodiments, the computer subsystem(s) are configured fordetermining locations on the specimen of the first and second subsets ofthe ROIs during the metrology process by aligning the output of thedetector to the design for the specimen. For example, the computersubsystems may be configured for automatic SEM-to-design fine alignment(e.g., using geometries in the FOV of the SEM). SEM-to-design finealignment may be performed since global alignment does not guaranteealignment of center lines of structures in images generated by ameasurement subsystem and design structures.

In some embodiments of aligning the output of the measurement subsystemto the design, imaginary center lines drawn through the patternedfeatures in the output and the design may be used for fine alignment(whereas the alignment marks described further herein may be used forglobal alignment of a wafer or one or more FOVs). FIGS. 7 and 8illustrate some issues that can arise when using edges of features inthe output and the design for alignment. For example, as shown in FIG.7, a portion of a design may include two features, line 700 and polygon702. In addition, a portion of output generated by measurement subsystemcorresponding to the portion of the design may include output for twofeatures, line 704 and polygon 706. The features in the design and theoutput of the measurement subsystem appear differently due to theprinting of the design on the water as described further above.

Output of the measurement subsystem (e.g., a SEM image) can be alignedto a design using edge-to-edge approaches at the upper edge or loweredge of a pattern of interest. For example, as shown in FIG. 7, if loweredges 708 of the horizontal portions of polygons 702 and 706 are usedfor alignment, then the line end measurements performed for polygon 706in areas 710 and 712 of the polygon will produce one measurement.However, if, as shown in FIG. 8, upper edges 800 of the horizontalportions of polygons 702 and 706 are used for alignment, then the lineend measurements performed for polygon 706 in areas 710 and 712 of thepolygon will produce a different measurement. In this manner, dependingon which edge of the polygon is used for alignment of the design to theoutput, the line end measurements will produce different results, whichis disadvantageous for a number of obvious reasons (e.g., the line endpull back measurements are inconsistent).

Instead of using edge-to-edge alignment, therefore, the embodimentsdescribed herein may perform alignment of measurement subsystem outputto design using the centers of the features in the output and in thedesign. For example, as shown in FIG. 9, if the centers of polygons 702and 706 are used for alignment, a different measurement will be producedfor line end measurements performed for polygon 706 in areas 710 and 712of the polygon than if either of the edge alignment methods describedabove are used. However, aligning the output of the measurementsubsystem and the design using the centers of the features will producea much more consistent alignment from ROI to ROI thereby providingsubstantially consistent measurements (e.g., corner measurements, lineend pullback measurements, and width measurements) for ROIs. Using thecenters of features for alignment rather than their edges can alsoimprove the robustness of the alignment for severely distorted patternsand when the FOV does not have many features for aligning the patternsof interest.

FIGS. 10-12 illustrate how the centers of patterned features in aportion of a design and in measurement subsystem output can be used foraligning the design to the output. For example, as shown in FIG. 10, aportion of a design for a specimen may include four different features,portions of lines 1000, 1002, and 1004 and polygon 1006. As furthershown in FIG. 10, an imaginary center line can be determined through theentirety of the portion of each feature included in the portion of thedesign. For example, imaginary center lines 1008, 1010, and 1012 may bedetermined for portions of lines 1000, 1002, and 1004. In addition,imaginary center line 1014 may be determined for polygon 1006. Theimaginary center lines may be determined in any suitable manner.

Imaginary center lines may also be determined for the patterned featuresas they appear in the measurement subsystem output. For example, asshown in FIG. 11, a portion of a design in measurement subsystem outputmay include four different features corresponding to those shown in FIG.10, e.g., portions of lines 1100, 1102, and 1104 and polygon 1106. Asfurther shown in FIG. 11, an imaginary center line can be determinedthrough the entirety of the portion of each feature included in thisportion of the design. For example, imaginary center lines 1108, 1110,and 1112 may be determined for portions of lines 1100, 1102, and 1104.In addition, imaginary center line 1114 may be determined for polygon1106. The imaginary center lines may be determined as described furtherherein.

Since the center lines of the patterned features in the design can bedetermined reproducibly and since the center lines of the patternedfeatures in the output should be able to be determined substantiallyreproducibly, the imaginary center lines can be used to align thepatterned features in the design to the patterned features in the outputrelatively reproducibly. For example, as shown in FIG. 12, alignment1200 of the center lines 1008 and 1108 can be used to reproducibly alignline 1000 in the design to line 1100 in the output. In another example,alignment 1202 of the center lines 1010 and 1110 can be used toreproducibly align line 1002 in the design to line 1102 in the output.In addition, alignment 1204 of the center lines 1012 and 1112 can beused to reproducibly align line 1004 in the design to line 1104 in theoutput. Furthermore, alignment 1206 of the center lines 1014 and 1114can be used to reproducibly align polygon 1006 in the design to polygon1106 in the output.

Of course, to align the features in a portion of the design to thefeatures in the same portion of the design in output of the measurementsubsystem, not all of the center lines of all of the features in theportion have to be aligned to each other in order to produce alignmentof all of the features to each other. For example, in the example shownin FIG. 12, alignment of the center lines of the polygon in the designand in the output may be used to produce fine design-to-output alignmentfor the polygon as well as the remaining features in this portion of thedesign. Reproducibly being able to align the features in the design tothe features in the measurement subsystem output will improve theconsistency of the measurements performed using the results of thealignment.

In a further embodiment, the parameter(s) of the measurement(s) includeboundaries of one or more dimensions across which the measurement(s) areperformed. For example, the computer subsystem(s) may be configured forautomatic generation of measurement bounds. The measurement bounds maybe automatically determined at runtime (no parameter needed duringsetup) for each unique site.

In some embodiments, the boundaries of the dimensions across which themeasurements are performed may be determined using the center linesdescribed further herein. For example, as shown in FIG. 13, a portion ofa design formed on a wafer may include four patterned features 1300,1302, 1304, and 1306, which are shown in FIG. 13 as they might be formedon the wafer and then imaged by the measurement subsystem, Imaginarycenter lines 1308, 1310, 1312, and 1314 may be generated for each of thefeatures as described further herein. Imaginary center lines may also begenerated for the spaces between the patterned features. The centerlines for the spaces may be defined by the midpoints between twoadjacent features in the design. For example, center line 1316 may bedefined based on the midpoints between the center lines of feature 1300and any other adjacent features (e.g., feature 1302). Center line 1318may be defined based on the midpoints between the center lines offeature 1302 and any other adjacent features on the left side of thisfeature (not shown in FIG. 13) and extending above feature 1300. Centerline 1320 may be defined based on the midpoints between the center linesof feature 1304 and any other adjacent features (e.g., features 1302 and1306). Center line 1322 may be defined based on the midpoints betweenthe center lines of features 1302 and 1306. In addition, center line1324 may be defined based on the midpoints between the center lines offeature 1306 and any adjacent features on the right side of this feature(not shown in FIG. 13). Although the center lines shown in FIG. 13 aredescribed as being defined with respect to the patterned features asthey appear in measurement subsystem output, the center lines may alsoor alternatively be defined based on the patterned features as theyappear in the design itself. In addition, although the center lines inthe spaces between the patterned features are described above as beingdefined based on the center lines in the patterned features, the centerlines in the spaces may be defined based on some other characteristic ofthe patterned features (e.g., the edges of the patterned features).

The center lines in the spaces between the patterned features may thenbe used as the boundaries for any measurements of the patterned featuresthat are performed. For example, as shown in FIG. 13, if a criticaldimension (CD) of patterned feature 1304 is to be measured for thispatterned feature, the measurement may be performed along one of lines1326 from the location of center line 1320 on one side of the patternedfeature to the location of center line 1320 on the other side of thepatterned feature and in a direction that is substantially perpendicularto center line 1312 within patterned feature 1304. In this manner, themeasurements may be performed in a direction that is orthogonal to thecenter lines through the patterned features. Although three lines 1326are shown in FIG. 13 representing the dimensions across which differentmeasurements may be performed for patterned feature 1304, any suitablenumber of such measurements may be performed at any suitable locationalong the center line within the patterned feature. In addition, themeasurements may be performed in a direction substantially parallel tothe center lines of the features. For example, as shown in FIG. 13,measurements may be performed along one of lines 1328 and, although notshown in FIG. 13, the boundaries of such measurements may also bedetermined by the center lines in the spaces between the patternedfeatures as described further herein. Furthermore, although not shown inFIG. 13, the dimensions across which the measurements are performed mayintersect the center lines of the patterned features and/or of thespaces between the patterned features at some angle other thanorthogonal (e.g., for measuring radius, for line end pullbackmeasurements, for line end distance measurements, etc.).

Using the center lines in the spaces between the patterned features asthe boundaries for any measurements performed on the patterned featuresmay advantageously ensure that the measurements begin and end outside ofthe patterned features thereby ensuring that the measurements areperformed across an entire dimension of the patterned features and thatthe boundaries of the measurements are sufficiently outside of thepatterned features such that the edges of the patterned features can bedetermined in the output generated during the measurements withsufficient accuracy and/or confidence. For instance, if the boundary atwhich a measurement begins is too close to the edge of a patternedfeature, the location of the edge of the patterned feature within theoutput may be easily confused with the measurement boundary and/or maybe missed in measurement boundary noise. However, using the center linesin the spaces between the patterned features to determine the boundariesof the measurements as described herein will substantially eliminate anysuch errors in patterned feature edge detection.

In a similar manner, if the measurements described herein are to beperformed for a space between two patterned features (e.g., to measurethe gap between two features), the boundaries for that measurement maybe determined based on the center lines within the patterned featuressurrounding the space. In this manner, the measurement can begin and endat locations sufficiently beyond the edges of the space thereby ensuringthat the measurement is performed across an entire dimension of thespace and that the edges of the space can be determined with relativelyhigh accuracy and/or confidence.

In one embodiment, the measurement(s) include automatically determininglocations in the output generated by the detector during themeasurement(s) of one or more edges of one or more structures formed onthe specimen. In this manner, the embodiments described herein may beconfigured for automatic determination of SEM edge locations. In someinstances, the edge locations may be determined using the 1D gradientprofiles described further herein. For example, edge locations may beautomatically determined by finding the strongest positive or negativegradient peaks within a 1D gradient profile. In other words, the peakpoints in the 1D gradient profile can be selected as the edge locations.A CD or other attributes of the features can then be determined based onthe edge locations. For example, the top, middle, or bottom CD can bedetermined by locating the top, middle, or bottom edge locations usingpositive/negative gradient peaks, zero crossing or negative/positivegradient peaks of 1D gradient profiles orthogonal to a line drawnthrough the center of the structure. However, the edges can be locatedusing other measurement algorithms besides using gradient profiles.

In another embodiment, the computer subsystem(s) are configured forautomatically generating one or more attributes for one of the first andsecond subsets of the ROIs based on results of the measurement(s). Inthis manner, the embodiments described herein may be configured forautomatic generation of measurement statistics and attributes for eachROI. The measurement statistics for each ROI may be determinedindependently from the metrology results for every other ROI. Variousmeasurement statistics (e.g., Max, Min, Mean, Average, Median, StandardDeviation, Range, and Sum) may be generated using multiple measurementswith a ROI. In another example, the computer subsystem(s) may beconfigured for automatic generation of other attributes such asone-dimensional (1D) gray scale profiles of a patterned structure formedon a wafer. The ID gray scale profiles may be automatically generated byoutput generated along a line that is either orthogonal to a center linethrough the patterned structure or parallel to the center line throughthe patterned structure. The computer subsystem(s) may also beconfigured for automatic generation of ID gradient profiles, which maybe automatically generated by taking a gradient of a ID gray scaleprofile determined as described above. In some instances, the multiplemeasurements within a ROI may include one measurement per 1D gray scaleor gradient profile. The measurement statistics may be related to actualCD, positive delta CD, and negative delta CD, where the delta CDprovides CD measurement relative to the design. In addition, varioustypes of gray scale or gradient-based attributes (such as peak localgray level difference, peak positive or negative gradient, etc.) using1D grayscale profiles parallel or orthogonal to a center line through astructure can be determined. The measurement statistics and/orattributes that can be determined using the embodiments described hereinare also not limited to the ones described herein.

In an additional embodiment, the one or more computer subsystems areconfigured for automatically generating one or more attributes formultiple instances of the ROIs in one of the first and second subsetsbased on results of the one or more measurements and comparing at leastone of the one or more attributes for two or more of the multipleinstances to identify outliers in the two or more of the multipleinstances. In this manner, the embodiments described herein may beconfigured for relative comparison of measurement statistics andattributes across various sites on a wafer to determine outliers.Measurement statistics and attributes for each of the ROIs can becompared across various sites on a wafer to determine outliers fordefect detection.

In a further embodiment, the one or more computer subsystems areconfigured for automatically selecting one or more alignment sites inthe design, and the metrology process includes determining one or morelocations of at least one of the one or more alignment sites on thespecimen during the metrology process and determining one or morelocations of one or more of the ROIs in the first and second subsets onthe specimen based on the one or more locations of the at least onealignment site on the specimen. For example, the embodiments describedherein may be configured for generating alignment sites (for coarsealignment) automatically with physical design analysis. In one suchexample, during metrology plan generation, for each FOV, the computersubsystem(s) may be configured to automatically determine uniquealignment site(s) and autofocus site(s) for each measurement site usingthe physical design. Automatically determining the unique alignmentsite(s) and autofocus site(s) may be performed using design analysisalgorithms and software.

In some embodiments, the systems described herein may be configured toexecute the metrology plan per FOV on a metrology tool that includes themeasurement subsystem and at least one of the computer subsystems. Inone such embodiment, the system may perform auto-focus per FOV and thenanchor point alignment per FOV. In some such instances, the system mayfetch design clips for the anchor point and measurement sites from adesign database to be used for auto-focus and/or anchor point alignment.The system may further be configured for measurement site alignment perFOV and execute the metrology plan for the measurement site such asperforming the selected types of measurements in ROI(s) within the FOV.The computer subsystem(s) may then produce measurement data per ROI.

In some embodiments, the metrology process includes determining if adefect is present in one of the ROIs in the first and second subsetsbased on only the one or more measurements performed in the one ROI. Inother words, the defect detection in an ROI may not be based on theoutput generated in any other ROI (in the same die as the ROI or in adifferent die than the one in which the ROI is located) or anymeasurements produced using such output. For example, a measurementresult generated for an ROI using only the output generated in that ROImay be compared to a threshold and any measurement result above thethreshold may be determined to be a defect while any measurement resultbelow the threshold may be determined to not be a defect (or viceversa). In addition, such defect detection may be performed using morethan one threshold (e.g., upper and lower thresholds) and/or any othersuitable defect detection method and/or algorithm.

In this manner, the metrology process for which the one or moreparameters are determined may include ROI-based single die defectdetection. Such defect detection may be performed to detect variousdefect types (e.g., pattern defects, missing and/or under-filledepitaxial layer, silicon germanium (SiGe) defects, etc.) by generatingvarious types of attributes at the ROI locations CD measurements,gradient magnitude, local gray level contrast, etc.).

In contrast to the embodiments described herein, currently used methodsfor ROI -based single die defect detection use a reference image orreference contours (acquired or generated) for defect detection. Theacquired image approach has half the throughput as compared to ROI-basedsingle die defect detection. The generated image or contour approachsuffers from complexity and inaccuracies of generating the reference.

In one embodiment, the one or more measurements performed in one of thefirst and second subsets of the ROIs include CD measurements of one ofthe ROIs relative to CD measurements of others of the ROIs. In thismanner, the measurements for which the one or more parameters aredetermined may be relative CD measurements in which the CD of multipleinstances of a given pattern of interest (POI) on a given wafer may becompared. In other words, the CD measurements may be a relativemeasurement rather than an absolute measurement. In contrast to theembodiments described herein, currently used methods for relative CDmeasurement use a CD-SEM tool where recipe setup to define multiple ROIsper site is a very manual and time consuming process and so asubstantially limited number of ROIs per site and a limited number ofunique sites per die can be measured for the CD measurements.

In an additional embodiment, the one or more measurements performed inone of the first and second subsets of the ROIs include overlaymeasurements of one of the ROIs relative to overlay measurements ofothers of the ROIs. In this manner, the measurements for which the oneor more parameters are determined may be relative overlay measurements.In other words, the overlay measurements may be a relative measurementrather than an absolute measurement. The overlay errors may be measuredduring multi-patterning fabrication processes (e.g., double, triple, orquad patterning), spacer pitch splitting fabrication processes, etc. Inaddition, the overlay errors may be measured between a current layerformed on the wafer and a previous layer formed on the wafer. Incontrast to the embodiments described herein, currently used methods forrelative overlay measurement use a CD-SEM tool where recipe setup todefine multiple ROIs per site is a very manual and time consumingprocess and so a substantially limited number of ROIs per site and alimited number of unique sites per die can be measured for the overlaymeasurements.

In some embodiments, the specimen includes a process windowqualification (PWQ) wafer, and the automatically generating includesautomatically generating the ROIs to be measured during the metrologyprocess based on the design and results of an inspection processperformed on the specimen. In this manner, the measurements for whichthe one or more parameters are determined may include automated reviewof pattern defects on PWQ wafers (e.g., using CD measurements), whichmay be detected by a PWQ inspection of the wafer performed by aninspection tool such as one of the inspection tools commerciallyavailable from KLA-Tencor. In some instances, the defects detected byPWQ inspection may be used as hot spots for metrology, and measurementsand detection performed at the metrology hot spots may be used forrefining the PWQ window (e.g., the window of process parameters forwhich PWQ is performed). Currently used methods for automated PWQ reviewof pattern defects perform manual or automated design-based review ofpattern defects found by a PWQ inspection. The manual method isinaccurate and unreliable (e.g., a user can miss complete patternfailures or can be unable to distinguish substantially subtle (e.g., 3to 7 nm) CD variation) and the design-based approach requires recipesetup between the discovery and metrology steps.

PWQ inspection may be performed as described in U.S. Pat. No. 6,902,855to Peterson et al. issued on Jun. 7, 2005, U.S. Pat. No. 7,418,124 toPeterson et al. issued on Aug. 26, 2008, U.S. Pat. No. 7,769,225 toKekare et al. issued on Aug. 3, 2010, U.S. Pat. No. 8,041,106 to Pak etal. issued on Oct. 18, 2011, and U.S. Pat. No. 8,213,704 to Peterson etal. issued on Jul. 3, 2012, which are incorporated by reference as iffully set forth herein. The embodiments described herein may include anystep(s) of any method(s) described in these patents and may be furtherconfigured as described in these patents. A PWQ wafer may be printed asdescribed in these patents.

In a further embodiment, the metrology process is performed on thespecimen during inline monitoring of a fabrication process performed onthe specimen. In this manner, the metrology process for which one ormore parameters are determined may include a metrology process that isperformed during inline monitoring (i.e., measurements performed on awafer produced by a production fabrication process). Such metrologyprocesses may be performed for measurements such as gate criticaldimension uniformity (CDU) measurements, line edge roughness (LER)/linewidth roughness (LWR) measurements, CD/overlay measurements, etc.

In another embodiment, the automatically generating includesautomatically generating the ROIs to be measured during the metrologyprocess based on the design and results of an inspection processperformed on the specimen. For example, inline monitoring may also beperformed for locations of defects detected by inspection such that thelocations of the detected defects are used essentially as “hot spots”for inspection guided metrology. In some such embodiments, the resultsof metrology may be correlated to the results of inspection. Forexample, in some instances, a pattern fidelity signature generated byinspection may be correlated to measurements performed during metrology.

In contrast to the embodiments described herein, the currently usedmethods for metrology during inline monitoring use a CD-SEM tool toperform CD/overlay measurements at specific metrology targets (e.g.,printed in the scribe lines on the wafer) and since the recipe setup isquite manual in defining ROIs, it is not able to automatically measurethousands of unique sites on a wafer. Some other currently used methodsfor inline monitoring include using a SEM review tool to randomly samplea few locations from millions of hot spot locations to perform criticalpoint inspection (CPI) using a die -to-die mode. However, since the hotspot locations are sampled randomly, the currently used methods can missa substantially large number of hot spot defects.

In an additional embodiment, the one or more computer subsystems areconfigured for comparing the one or more measurements performed in oneof the first and second subsets of the ROIs to design intent for the oneof the first and second subsets of the ROIs and modifying an opticalproximity correction (OPC) model based on results of the comparing. Inthis manner, the metrology process for which the one or more parametersare determined may be performed for OPC model verification againstdesign intent. In contrast to the embodiments described herein,currently used methods for OPC model verification against design intentuse a CD-SEM tool where recipe setup to define multiple ROIs per site isa very manual and time consuming process and so very limited number ofROIs per site and limited number of unique sites per die can be measuredfor CD measurements. For OPC, it is required to automatically discoverweak structures and immediately and/or automatically setup and measurethousands of unique sites per die.

In another embodiment, the one or more computer subsystems areconfigured for detecting defects in one of the first and second subsetsof the ROIs based on the one or more measurements and reporting the oneor more measurements as defect attributes for the detected defects. Inthis manner, the metrology process may include reporting patternfidelity measurements as defect attributes at the defect locationsreported by a redetection algorithm. In contrast to the embodimentsdescribed herein, currently used methods do not report measurementstatistics as part of defect attributes and so cannot quantify whether apattern distortion is a nuisance, partial break, full break, partialbridge, or full bridge.

The embodiments described herein have a number of advantages overcurrently used methods for determining one or more parameters for ametrology process. For example, the embodiments described herein providea substantially fast automated on -the-fly mechanism to generate ROIsfor thousands of unique sites and then automatically generate variousmeasurement statistics and attributes for each ROI across various sites(using SEM image and physical design clip for a given site), which couldthen be used to serve various use cases described herein.

Another embodiment relates to a computer-implemented method fordetermining one or more parameters of a metrology process to beperformed on a specimen. The method includes the automaticallygenerating and automatically determining steps described above.

Each of the steps of the method may be performed as described furtherherein. The method may also include any other step(s) that can beperformed by the measurement subsystem and/or computer subsystem(s) orsystem(s) described herein. The automatically generating andautomatically determining steps are performed by one or more computersystems, which may be configured according to any of the embodimentsdescribed herein. In addition, the method described above may beperformed by any of the system embodiments described herein.

An additional embodiment relates to a non-transitory computer-readablemedium storing program instructions executable on a computer system forperforming a computer-implemented method for determining one or moreparameters of a metrology process to be performed on a specimen. Onesuch embodiment is shown in FIG. 14. In particular, as shown in FIG. 14,non-transitory computer-readable medium 1400 includes programinstructions 1402 executable on computer system 1404. The computer-implemented method may include any step(s) of any method(s) describedherein.

Program instructions 1402 implementing methods such as those describedherein may be stored on computer-readable medium 1400. Thecomputer-readable medium may be a storage medium such as a magnetic oroptical disk, a magnetic tape, or any other suitable non-transitorycomputer-readable medium known in the art.

The program instructions may be implemented in any of various ways,including procedure-based techniques, component-based techniques, and/orobject-oriented techniques, among others. For example, the programinstructions may be implemented using ActiveX controls, C++ objects,JavaBeans, Microsoft Foundation Classes (“MFC”), SSE (Streaming SIMDExtension) or other technologies or methodologies, as desired.

Computer system 1404 may be configured according to any of theembodiments described herein.

Further modifications and alternative embodiments of various aspects ofthe invention will be apparent to those skilled in the art in view ofthis description. For example, methods and systems for determining oneor more parameters of a metrology process to be performed on a specimenare provided. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the invention. It is to beunderstood that the forms of the invention shown and described hereinare to be taken as the presently preferred embodiments. Elements andmaterials may be substituted for those illustrated and described herein,parts and processes may be reversed, and certain features of theinvention may be utilized independently, all as would be apparent to oneskilled in the art after having the benefit of this description of theinvention. Changes may be made in the elements described herein withoutdeparting) the spirit and scope of the invention as described in thefollowing claims.

What is claimed is:
 1. A system configured to determine one or moreparameters of a metrology process to be performed on a specimen,comprising: a measurement subsystem comprising at least an energy sourceand a detector, wherein the energy source is configured to generateenergy that is directed to a specimen, and wherein the detector isconfigured to detect energy from the specimen and to generate outputresponsive to the detected energy; and one or more computer subsystemsconfigured for: automatically generating regions of interest to bemeasured during a metrology process performed for the specimen with themeasurement subsystem based on a design for the specimen; andautomatically determining one or more parameters of one or moremeasurements performed in first and second subsets of the regions ofinterest during the metrology process with the measurement subsystembased on portions of the design for the specimen located in the firstand second subsets of the regions of interest, respectively, wherein theone or more parameters of the one or more measurements performed in thefirst subset are determined separately and independently of the one ormore parameters of the one or more measurements performed in the secondsubset.
 2. The system of claim 1, wherein said automatically generatingand said automatically determining are performed during setup of themetrology process.
 3. The system of claim 1, wherein said automaticallygenerating and said automatically determining are performed on-the-flyduring runtime of the metrology process.
 4. The system of claim 1,wherein said automatically generating comprises performing rules-basedsearching of the design during setup of the metrology process.
 5. Thesystem of claim 1, wherein the design for the specimen used for saidautomatically generating and said automatically determining does notinclude features of the design that will not be printed on the specimen.6. The system of claim 1, wherein the one or more computer subsystemscomprise a computer subsystem of an electronic design automation tool.7. The system of claim 1, wherein the one or more parametersautomatically determined for the first subset of the regions of interestresult in a first type of the one or more measurements performed in thefirst subset of the regions of interest, wherein the one or moreparameters automatically determined for the second subset of the regionsof interest result in a second type of the one or more measurementsperformed in the second subset of the regions of interest, and whereinthe first and second types of the one or more measurements are differentfrom each other.
 8. The system of claim 1, wherein the one or morecomputer subsystems are further configured for determining locations onthe specimen of the first and second subsets of the regions of interestduring the metrology process by aligning the output of the detector tothe design for the specimen.
 9. The system of claim 1, wherein the oneor more parameters of the one or more measurements comprise boundariesof one or more dimensions across which the one or more measurements areperformed.
 10. The system of claim 1, wherein the one or moremeasurements comprise automatically determining locations in the outputgenerated by the detector during the one or more measurements of one ormore edges of one or more structures formed on the specimen.
 11. Thesystem of claim 1, wherein the one or more computer subsystems arefurther configured for automatically generating one or more attributesfor one of the first and second subsets of the regions of interest basedon results of the one or more measurements.
 12. The system of claim 1,wherein the one or more computer subsystems are further configured forautomatically generating one or more attributes for multiple instancesof the regions of interest in one of the first and second subsets basedon results of the one or more measurements and comparing at least one ofthe one or more attributes for two or more of the multiple instances toidentify outliers in the two or more of the multiple instances.
 13. Thesystem of claim 1, wherein the one or more computer subsystems arefurther configured for automatically selecting one or more alignmentsites in the design, and wherein the metrology process comprisesdetermining one or more locations of at least one of the one or morealignment sites on the specimen during the metrology process anddetermining one or more locations of one or more of the regions ofinterest in the first and second subsets on the specimen based on theone or more locations of the at least one alignment site on thespecimen.
 14. The system of claim 1, wherein the metrology processcomprises determining if a defect is present in one of the regions ofinterest in the first and second subsets based on only the one or moremeasurements performed in the one region of interest.
 15. The system ofclaim 1, wherein said automatically generating comprises automaticallygenerating the regions of interest to be measured during the metrologyprocess based on the design and results of an inspection processperformed on the specimen.
 16. The system of claim 1, wherein the one ormore measurements performed in one of the first and second subsets ofthe regions of interest comprise critical dimension measurements of oneof the regions of interest relative to critical dimension measurementsof others of the regions of interest.
 17. The system of claim 1, whereinthe one or more measurements performed in one of the first and secondsubsets of the regions of interest comprise overlay measurements of oneof the regions of interest relative to overlay measurements of others ofthe regions of interest.
 18. The system of claim 1, wherein the specimencomprises a process window qualification wafer, and wherein saidautomatically generating comprises automatically generating the regionsof interest to be measured during the metrology process based on thedesign and results of an inspection process performed on the specimen.19. The system of claim 1, wherein the metrology process is performed onthe specimen during inline monitoring of a fabrication process performedon the specimen.
 20. The system of claim 1, wherein the one or morecomputer subsystems are further configured for comparing the one or moremeasurements performed in one of the first and second subsets of theregions of interest to design intent for the one of the first and secondsubsets of the regions of interest and modifying an optical proximitycorrection model based on results of said comparing.
 21. The system ofclaim 1, wherein the one or more computer subsystems are furtherconfigured for detecting defects in one of the first and second subsetsof the regions of interest based on the one or more measurements andreporting the one or more measurements as defect attributes for thedetected defects.
 22. The system of claim 1, wherein the specimencomprises a wafer.
 23. The system of claim 1, wherein the specimencomprises a reticle.
 24. The system of claim 1, wherein the energydirected to the specimen comprises light, and wherein the energydetected from the specimen comprises light.
 25. The system of claim 1,wherein the energy directed to the specimen comprises electrons, andwherein the energy detected from the specimen comprises electrons. 26.The system of claim 1, wherein the energy directed to the specimencomprises ions.
 27. A non-transitory computer-readable medium, storingprogram instructions executable on a computer system for performing acomputer-implemented method for determining one or more parameters of ametrology process to be performed on a specimen, wherein thecomputer-implemented method comprises: automatically generating regionsof interest to be measured during a metrology process performed for aspecimen with a measurement subsystem based on a design for thespecimen, wherein the measurement subsystem comprises at least an energysource and a detector, wherein the energy source is configured togenerate energy that is directed to the specimen, and wherein thedetector is configured to detect energy from the specimen and togenerate output responsive to the detected energy; and automaticallydetermining one or more parameters of one or more measurements performedin first and second subsets of the regions of interest during themetrology process with the measurement subsystem based on portions ofthe design for the specimen located in the first and second subsets ofthe regions of interest, respectively, wherein the one or moreparameters of the one or more measurements performed in the first subsetare determined separately and independently of the one or moreparameters of the one or more measurements performed in the secondsubset.
 28. A computer-implemented method for determining one or moreparameters of a metrology process to be performed on a specimen,comprising: automatically generating regions of interest to be measuredduring a metrology process performed for a specimen with a measurementsubsystem based on a design for the specimen, wherein the measurementsubsystem comprises at least an energy source and a detector, whereinthe energy source is configured to generate energy that is directed tothe specimen, and wherein the detector is configured to detect energyfrom the specimen and to generate output responsive to the detectedenergy; and automatically determining one or more parameters of one ormore measurements performed in first and second subsets of the regionsof interest during the metrology process with the measurement subsystembased on portions of the design for the specimen located in the firstand second subsets of the regions of interest, respectively, wherein theone or more parameters of the one or more measurements performed in thefirst subset are determined separately and independently of the one ormore parameters of the one or more measurements performed in the secondsubset, and wherein said automatically generating and said automaticallydetermining are performed by one or more computer systems.